The present invention relates to a cellular phone which communicates over a radio channel, and more particularly, to a cellular phone capable of smoothly reinitiating a call after disconnection of the radio channel.
A cellular phone which communications over a radio channel disconnects the channel when the telephone unit becomes incapable of communicating as a result of a drop in the field strength. Japanese-Patent Publication 5-276101 describes a cellular phone which terminates the call when there is a drop in the field strength and reinitiates a call when the field strength recovers to its original state.
Further, Japanese Patent Publication 5-276103 describes a cellular phone which, when the channel is disconnected, reinitiates a call by pressing a one-touch call reestablishment button. Until a predetermined period of time lapses after pressing of the one-touch button, the cellular phone automatically reinitiates the call every time the channel is disconnected. After lapse of the predetermined period of time, a call is not reinitiated unless the one-touch button is pressed again.
When a conventional telephone unit receives an incoming call, the telephone unit does not reinitiate the call even if the field strength recovers to its original state. For example, even if the telephone unit at the receiving end (hereinafter simply referred to as a "receiver telephone unit") assumes a responsibility for the deterioration of the field strength, e.g., when the receiver telephone unit is passing through a tunnel, and if the receiver telephone unit is capable of identifying whether or not the field strength is restored to its previous state by having finished passing through the tunnel, call reestablishment must be waited until the call originator reinitiates the call, thus delaying call reestablishment. If the call originator terminates call reestablishment while the channel is in a disconnected state, the call cannot be reinitiated unless the user of the receiver telephone unit dials the telephone number of the call originator.
Since the conventional cellular phone automatically reinitiates the call depending on whether or not the field strength has been restored without reference to the will of the user, there sometimes arises a case where the user leaves the telephone unit aside without knowing the fact that the channel was reconnected to the call originator.
If the field strength is not recovered for a long period of time after disconnection of the channel, there may arise a case where the user forgets that his telephone is waiting for call reestablishment after disconnection of the line.